Cu-based high-entropy two-dimensional oxide as stable and active photothermal catalyst

Cu-based nanocatalysts are the cornerstone of various industrial catalytic processes. Synergistically strengthening the catalytic stability and activity of Cu-based nanocatalysts is an ongoing challenge. Herein, the high-entropy principle is applied to modify the structure of Cu-based nanocatalysts, and a PVP templated method is invented for generally synthesizing six-eleven dissimilar elements as high-entropy two-dimensional (2D) materials. Taking 2D Cu2Zn1Al0.5Ce5Zr0.5Ox as an example, the high-entropy structure not only enhances the sintering resistance from 400 °C to 800 °C but also improves its CO2 hydrogenation activity to a pure CO production rate of 417.2 mmol g−1 h−1 at 500 °C, 4 times higher than that of reported advanced catalysts. When 2D Cu2Zn1Al0.5Ce5Zr0.5Ox are applied to the photothermal CO2 hydrogenation, it exhibits a record photochemical energy conversion efficiency of 36.2%, with a CO generation rate of 248.5 mmol g−1 h−1 and 571 L of CO yield under ambient sunlight irradiation. The high-entropy 2D materials provide a new route to simultaneously achieve catalytic stability and activity, greatly expanding the application boundaries of photothermal catalysis.

7. Ideally improve quality of several images (refer to marked manuscript) as they are mostly blurred 8. Throughout the manuscript, you may consider changing "hydrogenation performance" to "activity" 9. I suggest changing section's title (activity vs, performance) 10. 147. I would reword the sentence (see marked up manuscript) 11. 154 I would reword the sentence (see marked up manuscript) 12. Please, add error bars and uncertainty to all your graphs and data 13. Please, note that other minor comments to the language are included in the attachments

Reviewer #1 (Remarks to the Author):
This is a great paper on an emerging topic on catalysis. The advantage of high entropy materials was cleverly demonstrated. It can be published after consideration of the following items: (1) The temperature used in their "templated" synthesis of high entropy materials is only 450 °C. This is very low. Their XRD pattern is very broad, indicating very amorphous structures. I would suspect that the material is in a metastable state. I would like to the authors to comment on their crystallinity of their samples.

Response:
The authors thank for the reviewer's constructive comment. From our preparation experience, the crystallinity of 2D high entropy metal oxides largely depends on the type of metal element (alkaline earth metals (Mg, Ca) could enhance the crystallinity of 2D high entropy metal oxides), and is not significantly related to the annealing temperature. As shown in Supplementary Fig. 9, the pristine 2D Cu2Zn1Al0.5Ce5Zr0.5Ox and the 2D Cu2Zn1Al0.5Ce5Zr0.5Ox after 800 °C of RWGS have similar broaden XRD peaks. It indicates that the crystallinity of 2D Cu2Zn1Al0.5Ce5Zr0.5Ox has not clearly improved under high temperature treatment. In The originality of the work mainly lies in the composition of the 2D material, which, despite the inner complexity of the composition itself, seems to have been synthesized with quite widely available methods, which is positive and very significant to the field.
The work support the conclusions and claim. The materials' characterization has been thoroughly executed: the data and its interpretation is detailed and supported by different analytical approaches. I believe there is enough detail in the methods to be reproduced.
The DFT analysis backs up the experimental data. The DFT method is very well explained. So are the DFT data.
The methodology seems very sound, although I would suggest to add error bars and to mention very clear how data uncertainty was taken into account.
Said this, I have minor comments (which are also highlighted in the attachmentsdocuments marked up). The numbers at the beginning of each sentence include the manuscript line (see also attachment).

Response:
We are grateful for the reviewer's comprehensive review and suggestions.
We have revised the whole article according to your comments and highlight in blue color in the revised manuscript.

27. Revise language + unclear
Response: The authors thank for the reviewer's valuable suggestion, and we have revised this unclear sentence in the revised manuscript.
"and a PVP templated method is invented for generally synthesizing six-eleven dissimilar elements as high-entropy two-dimensional (2D) materials." 13. Please, note that other minor comments to the language are included in the attachments Response: Thanks for the reviewer's good suggestion, we have corrected unsuitable word according to the attachments.
"and a PVP templated method is invented for generally synthesizing six-eleven dissimilar elements as high-entropy two-dimensional (2D) materials." "The freeze-drying process was applied to obtain solids of 2D PVP micelles loaded with various metal ions." "which is the fingerprint feature of high-entropy materials." "Meanwhile, the instruments, chemicals, and steps required for this PVP templated method are simple and inexpensive." " Fig. 2a shows the RWGS CO production…" "It confirmed that using metal oxides such as CeO2 as support to introduce SMSI can weaken the sintering of Cu species."